Water Catchment and Roof Design

Source: bluegranola.com

A few years ago, I visited an off-grid strawbale house that was going to be featured on the USGBC’s GreenBuilt Tour. The house and woodworking shop were completely powered by solar energy. What interested me the most, though, was that all the water for domestic use was captured from the steep pitched roof, and grey water irrigated plants inside and out.

A gutter directed water to a 1500 gallon, below-ground cistern, which was essentially a basement. It was pumped up into the house and run through two filters, one finer than the other. This water was used for cooking, drinking, washing and flushing the toilet. It was tested regularly for the safety of the residents, and the owner told me it came back with good results every time. (Of course, otherwise they wouldn’t be ingesting it!)

Grey water from the kitchen and bathroom sinks, the shower and the washing machine ran to an indoor planter, and native plantings and a vegetable garden outside.

Water usage in the average home

The average US family uses 400 gallons of water a day. If you have a 1500-gallon supply with no regular rainfall, you are going to be very aware of your water use! Even 2500 gallons could go quickly. Conserving water is crucial when you are catching rainwater.

In our house design, we are toying with the idea of a butterfly roof for water catchment. This is beauty coupled with function. I love it!

Think of a butterfly roof as an inverted pitched roof. The side walls of the house are elevated, and the slopes of the roof meet in the center of the building, where there is a gutter. Rainwater drains to one side or the other, due to a slight angle.

Since our proposed space is so small (1024 sq ft), I knew the roof raised on the south side would make the interior appear larger. A butterfly roof would fit this idea. The north side could be trussed creating a flat ceiling inside. I also thought about raising the roof on the north side, too, to create a very unique ceiling throughout. Only more drawing will determine if that’s a good idea.

Other roof options for rain catchment

Other options include a regular pitched roof with an east-west axis with a gutter system on both sides running into one cistern. This would allow the perfect surface for solar panels, too. A ‘flat’ roof, seen on so many pueblo style houses here in the southwest, is the third option. It’s not really flat. There is a slight angle to one end, and water runs off through canales, metal spouts that drain the water into an unused area of the yard. This could be designed to fill a cistern.

These are just ideas. An architect, contractor or designer will have to look over my plans and figure out the details. Dreams don’t always translate into reality, especially in building! When you build or remodel, be sure to hire someone who knows how to do what you want. Otherwise, you may be teaching them about green features, and that never works out well!

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